Atomic force microscopy (AFM) was first described in 1986 by a group at Stanford and IBM, and quickly found application in investigating the material properties of surfaces. AFM was soon applied to biologically relevant samples, including proteins and DNA. Applications of scanning bacteria and viruses followed, and enabled topographic information to be collected at the nanoscale. Atomic force microscopy has made inroads into mammalian cell biology only in the past few years by analyzing: 1) nanomechanics, such as the mechanical stiffness of cells or their sensitivity to mechanical forces; 2) binding kinetics in force spectroscopy assays; 3) the structure of large macromolecular complexes; 4) the physical properties of biopolymers, including DNA, lipids, and proteins as they fold and unravel; and 5) receptor mapping in which molecules are localized on biological membranes.